Laser light stops require a nonreflecting surface, high damage thresholds, and a means to trap scattered light. An example of a prior art laser light stop or beam dump BD is shown in FIG. 1. A conical portion CP is enclosed within a light confining box BX such that a laser beam passing through an aperture portion AP in the box will impinge on the conical portion thereby scattering light within the confines of the box. The conical portion and the interior of the box are typically painted or anodized black to inhibit reflections. The most obvious drawbacks from this technique are that there is a low damage threshold of the paint or anodized surface and that the bulky enclosure is not suitable for insertion between spatially confining optical setups or micro-optical modules. As a consequence, there is a need for more suitable alternative light absorbing devices and surfaces.
The interrelationship between the absorbing and emitting properties of a body are derived from Kirchoff's law, i.e. the ratio of radiant emittance to absorptance is the same for all surfaces at the same temperature. In accordance with this law, polished metallic surfaces having high reflectance and hence low absorptance, also have low radiant emittance. For a body losing energy to its surroundings by radiation, the total emissive power is defined as the total energy emitted per second from one square centimeter of surface. Therefore, the increase in surface area of a body results in an increase in the emitted radiation.
In general, this energy is radiated over a range of wavelengths throughout the electromagnetic spectrum. This spectral distribution is dependent, in part, on the temperature of the body. By definition, a body which is a perfect absorber is called a blackbody. The energy radiated per unit area per unit time (W) of a blackbody at a given temperature (T) is given by the equation: EQU W=.sigma.(T.sup.4 -T.sub.0.sup.4),
where T.sub.0 is the temperature of its surroundings, and .sigma. is the Stefan-Boltzman constant (.sigma.=5.67.times.10.sup.-8 W/(m.sup.2 K.sup.4)). For a "gray" body, i.e. imperfect absorber and emitter, the total energy radiated per unit area per second (W.sub.gray) is given by: EQU W.sub.gray =e.sigma.(T.sub.A.sup.4 -T.sub.0.sup.4)
where T.sub.A is the actual temperature of the emitter, and e is the emissivity of the surface. Consequently, methods which increase the emissivity of a body therefore provide increased radiant energy for a given temperature, and more closely approximate a blackbody providing increased radiation efficiency.
Thus, in accordance with this inventive concept a need has been found to exist in the state of the art for a method to create a surface absorber or emitter which has applications in, for example, a laser light stop or microelectronic filaments, resistors and energy absorbing/emitting devices which overcomes the limitations inherent in the prior art as referred to above.